The Blackstone Twins Face Off vs. Destiny - The Blackstone Twins Saga, #1

Late in the 22nd century, twins Zoe and Zachary Blackstone are born into a world of nightly madness. Having lost their mother, they are dependent on their grandmother to guide them and a misfit band of wishful dreamers, as they journey hundreds of miles, in hope of finding a cure for the Night Madness, the mysterious affliction that takes all men. Zachary is doomed to share this fate, but for a rumor, a possible cure.
Struggling against the odds, and against dangerous wild animals, wild men, treacherous terrain, and a maniacal psychopathic woman, his twin sister Zoe is determined to help him discover this one hope of relief, so they can possibly return to a normal life, a thing of which they've only read about in books.